1. Field of the Invention
The present invention relates to a wrench for a fill cap for a portable fire extinguisher of the dry-chemical type, and particularly relates to a wrench for a fill cap with an upwardly projecting pressure indicator member.
2. Description of the Prior Art
A portable fire extinguisher consists of a container for an extinguishing agent, a pressure-producing device, and a mechanism such as a hose and a nozzle, for discharging and directing the extinguisher contents as required. The first modern portable fire extinguisher consisted of a metal cylinder filled with a solution of sodium bicarbonate and water beneath a container of sulfuric acid. When the extinguisher was inverted, the acid mixed with the solution to form carbon dioxide gas, which provided the pressure to expel the liquid through a hand-held hose.
Although such extinguishers represented a great improvement in fire fighting at the time of their introduction, they had many drawbacks and limitations. These earlier extinguishers were suitable only for certain types of fires such as Class A fires that involve ordinary combustibles such as paper, wood and cloth. These extinguishers have been substantially replaced by the multi-purpose, dry-chemical extinguisher that is effective on a wide range of fires including the fire classifications A, B, C and D as defined by the National Fire Protection Association. A typical modern multi-purpose dry-chemical extinguisher includes a steel tank or shell that can hold a quantity of dry-chemical, a pressure cartridge such as a CO.sub.2, cartridge that is mounted to the exterior of the tank, and which CO.sub.2, cartridge is connected by a controlling valve to the tank, for the purpose of pressurizing and "fluidizing" the dry contents of the reservoir when required. The fill cap is generally cylindrical in configuration and covers an opening of relatively large diameter in the top of the tank, the cap having external threads that engage the threaded opening in the tank top. When the cap is unscrewed and removed, the tank may be filled with an initial charge of selected fire-retardant dry chemical. When the extinguisher is used in fighting a fire and its dry chemical contents discharged, it is necessary to return the extinguisher to operational condition be refilling it with a certain amount of dry chemical, and providing a fresh CO.sub.2 cartridge. Thus, it is necessary to remove and then reattach the fill cap for the refilling of a unit. Popular designs of dry-chemical fire extinguishers that employ such fill caps are available under the trademarks Ansul, Redline, and others including General and Badger.
The upper part of such a fill cap is characterized by a diagonally extending flat surface and spaced-apart upward projections on opposite sides of the flat surface. The spacing between these upward projections provide a slot at each end of the diagonally extending flat surface, and in preferred models, there is an upwardly projecting cylindrical indicator at the center of the cap and in the middle of the flat surface. This indicator is mounted to the cap so as to move from a normal raised position to a lowered position which indicates that the extinguisher has been discharged, with a resulting loss in pressure, and is in need of servicing.
The above discussed multi-purpose extinguisher is maintained and serviced by certified individuals who are in need of an improved way for accomplishing their tasks in a reliable as well as quick and efficient manner. The drawback is the lack of a tool, device or fixture that is adept at loosening or tightening the fill cap described above. One device that is commonly used for this purpose includes a flexible strap that can embrace the cylindrical walls of the cap. While devices can be used to turn a cap, they can be unwieldly use, and require careful preparation and cleaning of engaging surfaces of both the cap and the strap in to prevent slippage. Another technique that is sometimes employed is the use of a hammer or similar tool in conjunction with a large screwdriver or the like to torque the cap in the desired direction by appropriately hammering the screw lever into the cap. Such practices are unsafe, noisy, unreliable, time consuming and can lead to damage of the extinguisher.